Welcome to the community, @Miranda_Glavin!
If you are using rating fields to collect the data, the data is already stored as numbers. So you can just create a formula field in Airtable that simply adds up all of the fields.
I can’t tell if you’re trying to provide the total to your form users, or just keep the totals in Airtable for yourself.
If you need to get the total to your form users, you can’t provide the total on the form itself. But after you create the formula field with the total, you can setup an automation to email them the total after the form is submitted.
If you need to display totals or formula results on your form itself, then you would need to use JotForm (which provides calculations), and possibly add in On2Air: Forms as well (which can pull in live data from your Airtable base).